Lateral variation in sandstone lithofacies from conventional core, Scotian Basin: implications for reservoir quality and connectivity <sup>1</sup>This article is one of a series of papers published in this CJES Special Issue on the theme of <i>Mesozoic–Cenozoic geology of the Scotian Basin</i>. <sup>2</sup>Geological Survey of Canada Contribution 20120021.
Bibliographic record
Abstract
Facies analysis in outcrops on land is strongly dependent on the lateral variability of lithofacies. Interpretation of conventional core in wells relies principally on the vertical succession of lithofacies. To better understand depositional environments and reservoir sandstone connectivity, the lithofacies of reservoir sandstones sampled in conventional core were correlated laterally through two sets of closely spaced wells in the Scotian Basin: in the Barremian–Albian succession around the Panuke–Cohasset field and in the Late Jurassic succession west of the Venture field. Regional correlation by gamma logs is confirmed by lithologically similar transgressive units including shelly mudstones or coals. A standard scheme of lithofacies and recognition of three types of parasequences were used for comparisons between wells. Some transgressive surfaces are of limited extent and may represent delta distributary switching and subsidence rather than regional changes in sea level. Major sandstone packets extend at least 10–30 km laterally, but commonly show lateral changes in lithofacies, and some are bounded by the margins of incised valleys. Such packages show poor correlation of lithofacies with porosity and permeability, probably because of the variable effects of diagenesis. Lateral transitions from tidal estuary sandstones in Panuke B-90 to thick-bedded river-mouth turbidites in Lawrence D-14, over a distance of 15 km, demonstrates the scale of delta lobes and confirms that sharp-based sandstone beds are turbidites related to river floods, not storm deposits. Similar lateral transitions in the Venture field are on a similar scale and pass distally into prodeltaic muddy landslide deposits.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.002 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".